Module mod_include

Summary

This module provides a handler which will process files
before they are sent to the client. The processing is
controlled by specially formated SGML comments, referred to as
elements. These elements allow conditional text, the
inclusion other files or programs, as well as the setting and
printing of environment variables.

Directives

Enabling Server-Side Includes

Any document with handler of "server-parsed" will be parsed by
this module, if the Includes option is set. If
documents containing server-side include directives are given
the extension .shtml, the following directives will make Apache
parse them and assign the resulting document the mime type of
text/html:

AddType text/html .shtml
AddHandler server-parsed .shtml

The following directive must be given for the directories
containing the shtml files (typically in a
<Directory> section, but this directive is
also valid .htaccess files if AllowOverride
Options is set):

Options +Includes

Alternatively the XBitHack
directive can be used to parse normal (text/html)
files, based on file permissions.

For backwards compatibility, documents with mime type
text/x-server-parsed-html or
text/x-server-parsed-html3 will also be parsed
(and the resulting output given the mime type
text/html).

Basic Elements

The document is parsed as an HTML document, with special
commands embedded as SGML comments. A command has the syntax:

<!--#element attribute=value
attribute=value ...-->

The value will often be enclosed in double quotes; many
commands only allow a single attribute-value pair. Note that
the comment terminator (-->) should be preceded
by whitespace to ensure that it isn't considered part of an SSI
token. Note that the leading <!--# is one
token and may not contain any whitespaces.

The allowed elements are:

config

This command controls various aspects of the parsing. The
valid attributes are:

errmsg

The value is a message that is sent back to the
client if an error occurs whilst parsing the
document.

sizefmt

The value sets the format to be used which displaying
the size of a file. Valid values are bytes
for a count in bytes, or abbrev for a count
in Kb or Mb as appropriate.

timefmt

The value is a string to be used by the
strftime(3) library routine when printing
dates.

This command prints one of the include
variables, defined
below. If the variable is unset, it is printed as
(none). Any dates printed are subject to the
currently configured timefmt. Attributes:

var

The value is the name of the variable to print.

encoding

Specifies how Apache should encode special characters
contained in the variable before outputting them. If set
to "none", no encoding will be done. If set to "url",
then URL encoding (also known as %-encoding; this is
appropriate for use within URLs in links, etc.) will be
performed. At the start of an echo element,
the default is set to "entity", resulting in entity
encoding (which is appropriate in the context of a
block-level HTML element, eg. a paragraph of text). This
can be changed by adding an encoding
attribute, which will remain in effect until the next
encoding attribute is encountered or the
element ends, whichever comes first. Note that the
encoding attribute must precede the
corresponding var attribute to be effective,
and that only special characters as defined in the
ISO-8859-1 character encoding will be encoded. This
encoding process may not have the desired result if a
different character encoding is in use. Apache 1.3.12 and
above; previous versions do no encoding.

exec

The exec command executes a given shell command or CGI
script. The IncludesNOEXEC Option disables this command
completely. The valid attributes are:

cgi

The value specifies a (%-encoded) URL relative path to
the CGI script. If the path does not begin with a (/),
then it is taken to be relative to the current
document. The document referenced by this path is
invoked as a CGI script, even if the server would not
normally recognize it as such. However, the directory
containing the script must be enabled for CGI scripts
(with ScriptAlias or
the ExecCGI Option).

The CGI script is given the PATH_INFO and query
string (QUERY_STRING) of the original request from the
client; these cannot be specified in the URL path. The
include variables will be available to the script in
addition to the standard CGI
environment.

For example:

<!--#exec cgi="/cgi-bin/example.cgi" -->

If the script returns a Location: header instead of
output, then this will be translated into an HTML
anchor.

The include
virtual element should be
used in preference to exec cgi. In particular,
if you need to pass additional arguments to a CGI program,
using the query string, this cannot be done with exec
cgi, but can be done with include
virtual, as shown here:

<!--#include virtual="/cgi-bin/example.cgi?argument=value" -->

cmd

The server will execute the given string using
/bin/sh. The include variables are available
to the command, in addition to the usual set of CGI
variables.

The use of #include
virtual is almost always
prefered to using either #exec cgi or #exec
cmd. The former (#include virtual) used the
standard Apache sub-request mechanism to include files or
scripts. It is much better tested and maintained.

In addition, on some platforms, like Win32, and on unix
when using suexec, you cannot pass arguments to a command in
an exec directive, or otherwise include spaces in
the command. Thus, while the following will work under a
non-suexec configuration on unix, it will not produce the
desired result under Win32, or when running suexec:

<!--#exec cmd="perl /path/to/perlscript arg1 arg2" -->

fsize

This command prints the size of the specified file, subject
to the sizefmt format specification.
Attributes:

file

The value is a path relative to the directory
containing the current document being parsed.

virtual

The value is a (%-encoded) URL-path relative to the
current document being parsed. If it does not begin with
a slash (/) then it is taken to be relative to the
current document.

flastmod

This command prints the last modification date of the
specified file, subject to the timefmt format
specification. The attributes are the same as for the
fsize command.

include

This command inserts the text of another document or file
into the parsed file. Any included file is subject to the
usual access control. If the directory containing the
parsed file has the Option
IncludesNOEXEC set, and the including the document would
cause a program to be executed, then it will not be
included; this prevents the execution of CGI scripts.
Otherwise CGI scripts are invoked as normal using the
complete URL given in the command, including any query
string.

An attribute defines the location of the document; the
inclusion is done for each attribute given to the include
command. The valid attributes are:

file

The value is a path relative to the directory
containing the current document being parsed. It cannot
contain ../, nor can it be an absolute path.
Therefore, you cannot include files that are outside of the
document root, or above the current document in the directory
structure.
The virtual attribute should always be used
in preference to this one.

The value is a (%-encoded) URL relative to the
current document being parsed. The URL cannot contain a
scheme or hostname, only a path and an optional query
string. If it does not begin with a slash (/) then it is
taken to be relative to the current document.

A URL is constructed from the attribute, and the output the
server would return if the URL were accessed by the client
is included in the parsed output. Thus included files can
be nested.

If the specified URL is a CGI program, the program will
be executed and its output inserted in place of the directive
in the parsed file. You may include a query string in a CGI
url:

<!--#include virtual="/cgi-bin/example.cgi?argument=value" -->

include virtual should be used in preference
to exec cgi to include the output of CGI
programs into an HTML document.

printenv

This prints out a listing of all existing variables and
their values. Starting with Apache 1.3.12, special characters
are entity encoded (see the echo element for details)
before being output. There are no attributes.

In addition to the variables in the standard CGI environment,
these are available for the echo command, for
if and elif, and to any program
invoked by the document.

DATE_GMT

The current date in Greenwich Mean Time.

DATE_LOCAL

The current date in the local time zone.

DOCUMENT_NAME

The filename (excluding directories) of the document
requested by the user.

DOCUMENT_URI

The (%-decoded) URL path of the document requested by the
user. Note that in the case of nested include files, this is
not then URL for the current document.

LAST_MODIFIED

The last modification date of the document requested by
the user.

USER_NAME

Contains the owner of the file which included it.

Variable Substitution

Variable substitution is done within quoted strings in most
cases where they may reasonably occur as an argument to an SSI
directive. This includes the config,
exec, flastmod, fsize,
include, and set directives, as well
as the arguments to conditional operators. You can insert a
literal dollar sign into the string using backslash
quoting:

<!--#if expr="$a = \$test" -->

If a variable reference needs to be substituted in the
middle of a character sequence that might otherwise be
considered a valid identifier in its own right, it can be
disambiguated by enclosing the reference in braces,
à la shell substitution:

<!--#set var="Zed" value="${REMOTE_HOST}_${REQUEST_METHOD}" -->

This will result in the Zed variable being set
to "X_Y" if REMOTE_HOST is
"X" and REQUEST_METHOD is
"Y".

EXAMPLE: the below example will print "in foo" if the
DOCUMENT_URI is /foo/file.html, "in bar" if it is
/bar/file.html and "in neither" otherwise:

The if element works like an
if statement in a programming language. The test condition is
evaluated and if the result is true, then the text until the
next elif,
else. or
endif element is included in the
output stream.

The elif or
else statements are be used the
put text into the output stream if the original test_condition
was false. These elements are optional.

Anything that's not recognized as a variable or an operator
is treated as a string. Strings can also be quoted:
'string'. Unquoted strings can't contain whitespace
(blanks and tabs) because it is used to separate tokens such as
variables. If multiple strings are found in a row, they are
concatenated using blanks. So,

The XBitHack directives controls the parsing of ordinary
html documents. This directive only affects files associated
with the MIME type text/html. XBitHack can take on
the following values:

off

No special treatment of executable files.

on

Any file that has the user-execute bit set will be
treated as a server-parsed html document.

full

As for on but also test the group-execute bit.
If it is set, then set the Last-modified date of the
returned file to be the last modified time of the file. If
it is not set, then no last-modified date is sent. Setting
this bit allows clients and proxies to cache the result of
the request.

Note: you would not want to use this,
for example, when you #include a CGI that
produces different output on each hit (or potentially
depends on the hit).